The present invention relates to antennas that can send and receive signals from a radio frequency device. In particular the present invention relates to antennas that are used in portable hand held devices.
An antenna is a transforming device that converts circuit currents into electromagnetic energy. Conversely, the antenna can convert electromagnetic energy into circuit currents. The frequency to which the antenna responds is based on characteristics of the antenna such as width and length. Changes in the width and length of the antenna affect the resistance of the antenna and shape the current densities along the length of the antenna. The antenna field can be affected by nearby objects, such as other antennas, which distort the performance of the antenna.
There remains a need for a portable hand-held communications device that implements an antenna in at least a transmitting or a receiving configuration. Ideally, the antenna conforms to the housing of the device and is positioned so that the antenna will transmit and receive regardless of the orientation of the device relative to the communications station.
An antenna system for a portable transceiver device comprises an antenna structure for transmitting and receiving RF signals. The antenna structure includes multiple feeding ports having a common structure fully coupling multiple antennas together. This antenna structure is made of a conductor that can be surface mounted over a nonplanar surface. When the conductor is mounted on a nonplanar surface, the antenna structure extends in three-dimensional space around the portable hand held communications device.
More accordingly, as a principal feature of the invention, an antenna system comprises an antenna structure, a first feeding port, and a second feeding port. The first and second feeding ports connect the antenna structure to communications circuitry. The antenna structure forms a first antenna structure connected to the first feeding port and further forms a second antenna structure connected to the second feeding port. Importantly, a portion of the first antenna structure is also a portion of the second antenna structure.
According to the present invention, there is also provided a portable communications device comprising: a transmitting circuit; a receiving circuit; and an antenna system, wherein the antenna system comprises a first antenna structure and a second antenna structure which has a common portion of a radiation element fully coupling the first antenna structure to the second antenna structure. Preferably, the first antenna structure and the second antenna structure include a monopole antenna, a dipole antenna, and a top loaded member wherein the top loaded member is a portion of the first antenna structure and the second antenna structure. Preferred applications of the present invention include portable communication devices, wireless PDAs, and two-way paging devices.
Some of the advantages provided by the present invention include: high efficiency, high gain, wide bandwidth, and low SAR. In addition, the present invention allows for use of one piece of wire to realize two different antenna functions simultaneously. Further still, the present invention""s use of two feeding points will allow optimization of the radio board layout to minimize EMI problems. Further and advantageously, there is no performance issue regarding coupling between antennas in the present invention as in traditional separate two antenna solutions wherein the coupling between the antennas degrades the antenna performance. Another advantage of the present invention is the simple layout. In the present invention a folded dipole is used as a transmitting antenna to raise the antenna radiation resistance thereby increasing efficiency. Traditional dipoles and monopoles that are widely used in wireless devices are very sensitive to a change in the environment. In contrast, the present invention is less sensitive to the environment by taking advantage of the environment by reducing the effects of the same. Further still, the present invention allows the potential for increasing bandwidth by appropriately changing wire lengths. Finally, the present invention allows for lower manufacturing cost due to simpler layout.